Semiconductor components such as dice, and interconnects for electrically engaging dice, can include high aspect ratio features. A "high aspect ratio feature" means that a height, or depth, of the feature is several times greater than a width, or diameter, of the feature. For example, features having aspect ratios (e.g., height/width) of about 5 or more, are sometimes considered high aspect ratio features.
One example of a semiconductor component that includes high aspect ratio features is the interconnect described in U.S. Pat. Nos. 5,483,741 and 5,686,317 to Akram et al. This interconnect includes contact members adapted to electrically engage corresponding contact locations on a semiconductor die for testing. The contact members on the interconnect include projections etched on a silicon substrate. A representative height of the projections, measured from the surface of the substrate to the tips of the projections, can be between about 3 to 10 mils. A representative width of each side of the projections can be from 0.5 to 5 mils.
During fabrication of the interconnect, the projections must be covered with an electrically conductive layer. One method for forming the conductive layer includes a lithographic process, in which a metal is blanket deposited on the substrate, then etched using a photopatterned layer of resist. Typically, the resist is applied using a spin coater, which is adapted to apply a quantity of resist as the substrate is spun to distribute the resist.
This type of high aspect ratio feature is difficult cover with metal using conventional lithographic processes. In particular problems can occur because the resist tends to slide off the sidewalls and tips of the projections, and to pool on the surface of the substrate. This phenomena is sometimes referred to as poor step coverage. A thickness of the resist layer can also be uneven due to the uneven topography of the substrate. The poor step coverage, and unevenness of the resist layer, can produce defects during photopatterning of the resist to form an etch mask. The defects in the etch mask can produce defects in the subsequently formed conductive layer. In particular, the metal on contact projections not protected by resist can be etched away, so that portions of the projections are not covered with metal.
Components other than interconnects, such as semiconductor dice can also include high aspect ratio features that must subsequently be covered with a photopatterned metal layer. For example, U.S. Pat. No. 5,354,705 to Matthews et al. discloses a method for fabricating semiconductor container structures having a high aspect ratio. The container structures function to provide an increased surface area for storage capacitors. When it is necessary to apply photoresist to these non-planar topographies, conventional resist deposition and photopatterning processes can provide poor results. Specifically, the photoresist may not form with a uniform thickness over the non-planar features, and may not cover the tips and sidewalls of the features. When a metal layer covering the container structures is subsequently patterned, defects can occur.
The present invention is directed to an improved method for fabricating semiconductor structures having high aspect ratio features.